#include <math.h> #include "stat.h" void update_stats(struct stats *stats, u64 val){	double delta; 	stats->n++;	delta = val - stats->mean;	stats->mean += delta / stats->n;	stats->M2 += delta*(val - stats->mean); 	if (val > stats->max)		stats->max = val; 	if (val < stats->min)		stats->min = val;} double avg_stats(struct stats *stats){	return stats->mean;} /* * http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance * *       (\Sum n_i^2) - ((\Sum n_i)^2)/n * s^2 = ------------------------------- *                  n - 1 * * http://en.wikipedia.org/wiki/Stddev * * The std dev of the mean is related to the std dev by: * *             s * s_mean = ------- *          sqrt(n) * */double stddev_stats(struct stats *stats){	double variance, variance_mean; 	if (stats->n < 2)		return 0.0; 	variance = stats->M2 / (stats->n - 1);	variance_mean = variance / stats->n; 	return sqrt(variance_mean);} double rel_stddev_stats(double stddev, double avg){	double pct = 0.0; 	if (avg)		pct = 100.0 * stddev/avg; 	return pct;}